A vehicle using an internal combustion engine uses gasoline or heavy oil as main fuel which causes pollutions such as air pollution. Recently, therefore, to reduce such pollutions, environmentally friendly vehicles have been developed. The eco-friendly or environmentally friendly vehicle is a type of vehicle that uses a battery engine operated by electric energy output from a battery. The eco-friendly vehicle uses a battery pack, in which a plurality of secondary battery cells which may be charged and discharged are formed in one pack, as a main power source. Therefore, the eco-friendly vehicle prevents the discharge or exhaust gas and generates minimal noise.
In particular, to supply power output to the battery pack to an auxiliary battery, the eco-friendly vehicle includes a low voltage direct current-direct current (DC-DC) converter (LDC), a converter controller configured to operate the LCD, a sensor configured to sense the auxiliary battery to generate state of battery information. However, a voltage control effect of the low voltage converter may not be constant due to errors of the state of battery information (e.g., state of charge (SOC)) generated by the sensor. In other words, the SOC generated by the sensor (e.g., intelligent battery sensor (IBS)) is 85% and a fuel efficiency effect is 1%, but actually, the SOC is 75% and the fuel efficiency effect is only 0.5%. Further, durability performance of the battery may be reduced. For example, the SOC generated by the sensor is 80 to 100% and durability cycle lifespan is 100%, but actually, the SOC is 70 to 100% and the durability cycle lifespan is only 90%.